The present invention relates to a disc manufacturing method, a data recording apparatus, an information recording medium, an information processing apparatus and method, and a computer program. More specifically, the present invention relates to a disc manufacturing method, a data recording apparatus, an information recording medium, an information processing apparatus and method, and a computer program, which make it possible to prevent unauthorized use of content in the form of pirated discs and to track down the original manufacturer of pirated discs.
In recent years, information recording media that can store large volumes of data, such as a DVD (Digital Versatile Disc) and a BD [Blu-ray Disc (trademark)], are becoming increasingly commonplace. Digital data such as high-definition image data is recorded onto these large-capacity discs.
Since digital data can be repeatedly recorded and reproduced without degradation of image or sound quality, distribution of unauthorized copies of content via the Internet, and circulation of pirated discs produced by copying content onto recording media such as a CD-R and a DVD have become a major problem.
In particular, a problem that has arisen recently is the practice in which proper DVD manufacturing equipment is set up, a stamper is prepared on the basis of a legitimate commercial DVD disc, and a large quantity of pirated discs are mass-produced on the basis of the stamper and circulated. Further, with regard to legitimate licensed disc plants as well, the problem of illicit manufacture and sales of discs has arisen, in which more discs than approved by a license are illicitly produced, and surplus discs are sold without consent. Circulation of such illicitly produced discs constitutes an infringement on the copyright of content, and some preventive measures are required.
A manufacturing process for a disc such as a DVD or BD will be described with reference to FIG. 1. FIG. 1 is a diagram illustrating the manufacturing process of an information recording medium storing content whose usage is permitted on the basis of a legitimate content usage right, for example, ROM discs such as a DVD or a BD disc. As shown in FIG. 1, content is delivered from a content owner 11 who owns the content to a content authoring entity 12 which performs content authoring and undergoes authoring, thereby generating authored content for disc recording. Thereafter, a disc 50 to be circulated into the market is produced at a disc manufacturing plant 20.
The content owner 11 delivers, together with the content, usage control information (Usage Rule) that sets forth the usage right for the content, to the content authoring entity 12. The usage control information (Usage Rule) is set in correspondence with the content, for example, and includes information as to whether or not copying of the content is allowed. The usage control information is also stored together with the content onto a disc 30 that is finally delivered to the user. When using the content with a user device such as a reproducing apparatus, a content usage application executed on the user device refers to the usage control information, and executes the use of the content in compliance with the usage control information.
The disc manufacturing plant 20 receives the authored content from the content authoring entity 12 and the usage control information (Usage Rule), and further receives key information to be applied to content encryption and decryption from a licensing entity 13 that performs content usage management. The licensing entity 13 carries out content usage management, and generates various kinds of key data such as MKB (Media Key Block) and media key (Km) and provides these pieces of data to the disc manufacturing plant 20.
An MKB (Media Key Block) is an encryption key block generated on the basis of a tree-structure key distribution scheme known as one type of a broadcast encryption scheme. The MKB is a key information block allowing the acquisition of a media key (Km), which is a key necessary for decryption of content, only by processing (decryption) based on a device key (Kd) stored in an information processing apparatus of a user having a valid license. The MKB represents an application of an information distribution scheme according to a so-called hierarchical tree structure. The acquisition of the media key (Km) is allowed only when the user device (information processing apparatus) has a valid license, and the media key [Km] cannot be acquired by a revoked user device.
The licensing entity 13 can generate an MKB configured so that, through a change of the device key used for encryption of key information stored in the MKB, decryption, that is, acquisition of a media key required for content decryption, cannot be performed with a device key stored in a specific user device. Accordingly, it is possible to provide encrypted content that can be decrypted only with respect to a device with a valid license by revoking an unauthorized device at arbitrary timing.
In the disc manufacturing plant 20, a formatter 31 executes such processing as content encryption and formatting of each piece of data. Further, after executing the preparation of a master or stamper by a cutting machine 32, the disc 50 is manufactured by a replicator 33 by using the prepared stamper. The disc manufacturing plant 20 manufactures the number of discs 50 permitted by the licensing entity 13.
Content encryption and generation of disc-stored data executed by the formatter 31 will be described with reference to FIG. 2. FIG. 2 shows processing at the disc manufacturing plant 20, and processing by an information processing apparatus (reproducing apparatus) 60 as a user device that uses data stored in the information recording medium (disc) 50 and content stored in the information recording medium (disc) 50.
It should be noted that in FIG. 2, processing by the cutting machine 32 and the replicator 33 shown in FIG. 1 is omitted. Basically, data generated by the formatter 31 is stored onto the information recording medium (disc) 50. Now, processing at the disc manufacturing plant 20 shown in FIG. 2 will be described.
As described above, the MKB 21 is an encryption key block received from the licensing entity 13, and allows a media key (Km) to be extracted by processing with a device key (Kd) 61 stored in a memory of the user device with a legitimate license, that is, the information processing apparatus (reproducing apparatus) 60 shown in FIG. 2.
The MKB21 is stored in the information recording medium (disc) 50. This corresponds to an MKB 51 in the drawing. A volume ID 22 is an identifier (ID) set for a predetermined number of discs as a unit, and is generated by a random-number generation process or the like at the disc plant 20. The volume ID 22 is recorded with respect to the information recording medium (disc) 50. This corresponds to a volume ID 52 in the drawing. The volume ID 52 is recorded in a format different from the data recording format that can be realized by a standard recording apparatus as a user device. That is, data writing employing special signal processing is performed. Special signal processing is also required for data recording. For example, the ROM-mark scheme (side-channel scheme) or the like is employed.
Further, at the disc manufacturing plant 20, in step S11, a media key (Km) 23 received from the licensing entity 13, and the volume ID 22 are concatenated, and a hash value is calculated in step S12, thus generating a volume-unique key (Kuv). Further, in step S13, the hash value of usage control information (Usage Rule) 25 corresponding to disc-stored content is calculated, and in step S14, an exclusive-OR of a title key (Title Key) 24 set in correspondence with the content and generated through random-number generation or the like at the disc plant 20, and the hash value of the usage control information is calculated. The result of this exclusive-OR operation is encrypted with the volume-unique key (Kvu) generated on the basis of the volume ID 22 and the media key (Km), and is stored onto the information recording medium 50. This corresponds to an encrypted key (Encrypted Key) 53 in the drawing. The encrypted key (Encrypted Key) is encrypted data obtained based on the title key 24 and the hash value of the usage control information 25.
Further, the usage control information 25 is also stored onto the information recording medium 50. This corresponds to usage control information 54 shown in the drawing. Content 26 is authored content generated by the content authoring entity 12 described above with reference to FIG. 1. Encryption of the content 26 is executed with the title key 24 in step S16, and the content 26 is stored onto the information recording medium 50 as encrypted content 55.
As a result, as shown in the drawing, the information recording medium (disc) 50 stores the MKB 51 as the encryption key block storing the media key [Km], the volume ID 52 written by special signal processing, the encrypted key 53, the usage control information (Usage Rule) 54, and the encrypted content 55.
The information recording medium 50 is loaded into the information processing apparatus (reproducing apparatus) 60 as a user device. By executing a predetermined data reproducing application, a preset processing sequence is executed to thereby perform reproduction of content.
First, in step S21, the information processing apparatus (reproducing apparatus) 60 executes the processing of the MKB 51 read from the information recording medium 50, by using the device key (Kd) stored in the memory of the information processing apparatus (reproducing apparatus) 60. It should be noted that to acquire the media key (Km) from the MKB 51, it is necessary to use a device key (Kd) that is stored in an information processing apparatus having a valid license. A user device that has been revoked cannot acquire the media key (Km).
Next, in step S22, the media key (Km) acquired from the MKB and the volume ID read from the information recording medium 50 are concatenated, and in step S23, the hash value is calculated, thereby generating a volume-unique key (Kvu).
Next, in step S24, decryption of the encrypted key (Encrypted Key) 53 read from the information recording medium 50 is executed with the volume-unique key (Kvu) thus generated. Further, in step S25, the hash value of the usage control information 54 read from the information recording medium 50 is calculated. In step S26, an exclusive-OR operation between this hash value and the decrypted result of step S24 is executed.
The processing of steps S24 to S26 corresponds to a process reverse to the steps S13 to S16 executed at the disc manufacturing plant 20. A title key is calculated through the processing of steps S24 to S26. In step S27, using the title key thus generated, decryption of the encrypted content 55 read from the information recording medium 50 is executed, and content 62 is outputted.
As described above, various kinds of data are stored in the information recording medium 50 so as to allow usage of content only by a user device having a legitimate license. At the disc manufacturing plant 20, necessary data is received from the licensing entity 13 and the content authoring entity 12, and processing according to a predetermined process is executed to manufacture the information recording medium 50. On the other hand, on the side of the information processing apparatus 60 as a user device as well, processing according to a predetermined sequence is performed, thereby enabling decryption and reproduction of content.
However, as described above, pirated discs are manufactured through various processes and circulated. Referring to FIGS. 3 to 6, description will be given of a plurality of ways in which pirated discs are manufactured.
There are the following ways to manufacture pirated discs.
(1) Production of pirated discs through production of more discs than permitted by a license
(2) Production of pirated discs by using a diverted stamper
(3) Production of pirated discs on the basis of copying of a read signal (RF signal) from a legitimate commercial disc
(4) Production of pirated discs by physically copying a pit pattern from a legitimate commercial disc
These processes will be described below.
FIG. 3 is a diagram illustrating the process (1) production of pirated discs through production of more discs than permitted by a license. The disc manufacturing plant 20 is a plant that possesses a legitimate license and for which production of the disc 50 is permitted on the basis of the legitimate license. However, according to this process, pirated discs 70 are produced by producing more discs than permitted by the license, and are sold through illicit channels.
FIG. 4 is a diagram illustrating the process (2) production of pirated discs by using a diverted stamper. The disc manufacturing plant 20 is a plant that possesses a legitimate license and for which production of the disc 50 is permitted on the basis of the legitimate license. However, according to this process, the stamper manufactured with the cutting machine 32, that is, the stamper in which formatted data is recorded is diverted to a pirated-disc manufacturing plant 80, and the pirated discs 70 are produced using a replicator 81 installed in the pirated-disc manufacturing plant 80.
FIG. 5 is a diagram illustrating the process (3) production of pirated discs on the basis of copying of a read signal (RF signal) from a legitimate commercial disc. According to this process, unlike in the processes (1) and (2), the pirated discs 70 are produced using the legitimate commercial disc 50.
A pirated-disc manufacturing plant 90 loads the legitimate commercial disc 50 into a reader 91, and performs reading of an RF signal from the legitimate disc 50. An RF signal is a signal obtained by conversion from a read optical signal from the disc 50 that has not been converted into a reproduction signal. This RF signal is inputted to a cutting machine 92 for preparing a master or stamper to manufacture a stamper, and a large number of pirated discs 70 are produced using a replicator 93.
FIG. 6 is a diagram illustrating the process (4) production of pirated discs by physically copying a pit pattern from a legitimate commercial disc. As in the process (3), in this process as well, the pirated discs 70 are produced using the legitimate commercial disc 50.
According to this process, a pirated-disc manufacturing plant 95 loads the legitimate commercial disc 50 into a disc separating device 96, and separates the protective film and the reflective film on the surface of the disc 50. The pit pattern on the disc becomes fully exposed by this process. Then, the pit pattern is physically copied by a transfer device 97, thereby forming a stamper. Thereafter, a large number of pirated discs 70 are produced with this stamper by using a replicator 98.
As described above, there are various techniques for manufacturing pirated discs. Effective measures for preventing the use of such techniques are being desired.